Thin floss brush

ABSTRACT

A dental floss brush made from a reverse twisted, high tenacity nylon yarn comprising at least two thread sections having diameters, in their relaxed state, of at least 2.5 min. The thread sections are separated by a floss brush section integral therewith having a diameter of from up to 4 mm in its relaxed state and a diameter of from 1.7 to 3.0 mm under a tension of 0.05N. The brush floss has a breaking strength of at least 5N. The floss brush section can be coated with a low melting wax composition, optimally a polyethylene glycol ester of beeswax alone or in combination with a flavoring oil, silicone oil lubricant or mixtures thereof. This product is made by coating a reverse twisted, high tenacity nylon yarn with a solution of polymer in a volatile solvent, the polymer being selected from the group consisting of nylon, polyurethane and mixtures thereof. Then the solvent is selectively vaporized from thread portions of the yarn while preventing significant vaporization of solvent from brush portions of the yarn, while the yarn is maintained under a tension of from 0.15 to 1N. The brush portions of the yarn are steam treated while the yarn is under a tension of approximately zero until the brush portions of the yarn have regained at least 100 percent of the diameter of the uncoated, relaxed yarn. Residual solvent is then removed from the brush portions of the yarn while the yarn is under a tension of approximately zero.

This application is a continuation of application Ser. No. 08/151,707,filed on Nov. 12, 1993, now abandoned, which is in turn a continuationof application Ser. No. 07/883,511 filed May 15 , 1992, now U.S. Pat.No. 5,284, 169.

FIELD OF THE INVENTION

This invention relates to an improved thin floss brush product and to anovel process for its manufacture. In particular this invention isdirected to an improved floss brush made of a textured, high tenacitynylon yarn which provides the scraping functions of a floss under hightension and the brushing functions of a yarn under low tension.

BACKGROUND OF THE INVENTION

Tooth decay and dental disease can be caused by bacterial actionresulting from the formation of plaque about the teeth and/or theentrapment of food particles between the teeth and intersticestherebetween. The removal of plaque and entrapped food particles reducesthe incidence of caries, gingivitis, and mouth odors as well asgenerally improving oral hygiene. Conventional brushing has been foundto be inadequate for removing all entrapped food particles and plaque.To supplement brushing, dental flosses and tapes have been recommended.The term "dental floss", as used herein, is defined to include bothdental flosses, dental tapes and any similar article.

To improve the effectiveness and convenience of dental flosses, dentalflosses combining a thin "floss" portion and a thickened "brush"portion, together with a threader have been developed. The brushportion, when drawn between tooth surfaces, has been found to provide animproved cleaning action which removes materials left by the flossportion, when used alone. The combination provides a substantiallysuperior cleaning action. Such a device is described in U.S. Pat. No.4,008,727, for example. The complexity of this product requires thateach floss segment be individually manufactured and that the product bepackaged as bundles of the individual, separate floss articles.

A continuous yarn having brush segments separated by thinner segments isdisclosed in U.S. Pat. Nos. 4,008,727 and 4,142,538. However, productsformed using conventional textured nylon yarns and previously developedmanufacturing processes were not satisfactory. Manufacture of brushfloss products of this type involves applying a polymer solution to theyarn. The solvent is then selectively evaporated from the thinnedsegment portion while avoiding solvent evaporation from the brushportion, the yarn being maintained under high tension during thisprocedure. The solvent in the brush portion is then removed while theyarn is relaxed, that is, under low or no tension. Thin yarn products ofmost texturizing processes were found to be too weak to be placed underthe high tension required for forming the desired thin section.Furthermore, the polymer impregnated brush portion did not regain itsoriginal bulk and texture when the tension was relaxed prior to solventremoval from the brush portion.

Attractive and pleasant flavors and flavor odors have been provided indental products including dental flosses to impart a flavor to theflosses and encourage their regular use. These have been applied in theform of flavoring oils to the surface of floss or wax coating on thefloss, or dispersed in wax coatings applied to the floss. In a processdescribed in copending, commonly assigned application Ser. No.07/809,625 filed Dec. 17, 1991, flavoring oils are applied to floss in alow-melting wax composition containing a mixture of high and low meltingpoint polyethylene glycols, the low melting characteristic of the waxretaining the flavoring oils without significant loss throughevaporation or from oxidation. Application of these compositions to afloss brush was found to be unsatisfactory because they clogged andmatted the yarn, reducing its value as a brush cleaning article.

OBJECTS AND SUMMARY OF THE INVENTION

It is one object of this invention to provide an improved floss brushwhich can be spooled and dispensed as a continuous brush/thread from atraditional floss dispenser.

It is another object of this invention to provide a polymer coated flossbrush made from a textured yarn which retains substantially all of thebulk and thickness of the original, uncoated, relaxed yarn.

It is still a further object of this invention to provide a floss brushwith a high flavor content.

The dental floss brush of this invention is made from a reverse twisted,high tenacity nylon yarn. It comprises at least two thread sectionshaving diameters, in their relaxed state, of less than 2.5 mm preferablyless than 1.35 mm. The thread sections are separated by a floss brushsection integral therewith of yarn having a diameter of from 2 to 4 mm,preferably from 2.4 to 3.5 mm, in its relaxed state and a diameter offrom 1.7 to 3.0 mm under a tension of 0.05N (newtons). The brush flosshas a breaking strength of at least at least 5N and preferably above20N. Optimally, the yarn has a breaking strength of at least 35N; thethread sections have diameters, in their relaxed state, of less than 50percent of the diameter of relaxed, uncoated yarn from which they wereformed; the floss brush has, in its relaxed state, at least 100 andpreferably at least 220 percent of the original diameter of relaxed,uncoated yarn from which it was formed; and each floss brush section hasa diameter under a tension of 0.05N of at least 60 percent, preferablyabove 75 percent, and optimally above 150 percent of the relaxeduncoated yarn from which it was formed.

In one embodiment, the floss brush is coated with a low melting waxcomposition, optimally a polyethylene glycol ester of beeswax, alone orin combination with a flavoring oil, silicone oil lubricant or mixturesthereof.

In summary, one process of this invention is a process for manufacturinga continuous length of dental floss brush comprising alternatingsequences of thread portions and floss brush portions integraltherewith. The process comprises the steps of

a) coating a reverse twisted high tenacity nylon yarn with a solution ofpolymer in a volatile solvent, the polymer being selected from the groupconsisting of nylon, polyurethane and mixtures thereof;

b) selectively vaporizing solvent from thread portions of the yarn whilepreventing significant vaporization of solvent from brush portions ofthe yarn, while the yarn is maintained under a tension of from 0.15 to1N;

c) steam treating the brush portions of the yarn while the yarn is undera tension of approximately zero until the brush portions of the yarnhave regained at least 100 percent and preferably at least 220 percentof the diameter of the uncoated, relaxed yarn; and

d) removing residual solvent from the brush portions of the yarn whilethe yarn is under a tension of approximately zero.

Preferably, the solution of polymer comprises from 5 to 15 wt.%polyurethane and from 5 to 15 wt.% nylon. Optimally, the solvent is anaqueous ethanol solution containing at least 57 wt.% ethanol. Optimally,the steam treatment is conducted at a temperature of from 80° to 105° C.The solvent can be selectively vaporized from thread portions of theyarn by exposing the thread portions to heat while shielding the brushportions adjacent thereto with heat insulators.

Optionally, the process includes the additional steps of coating thethreads of the brush portion of the product of step (d) with low meltingwax without clogging the openings thereof. This can be effected byapplying the coating as a liquid wax at a temperature of from aboveabout 50° up to 80° C., removing excess portions of the wax, and coolingthe coated brush portions to a temperature below 50° C. The low meltingwax, preferably a polyethylene glycol ester of beeswax, can be usedalone or in combination with a flavoring agent, silicone oil lubricantor mixtures thereof.

The process of this invention for restoring the bulk of stretched yarncoated with a polymer solution following relaxation of tension thereoncomprises the step of treating the yarn with steam while the yarn isunder a tension of approximately zero until the brush portions of theyarn have regained at least 100 and preferably 220 percent of thediameter of the uncoated, relaxed yarn.

The process of this invention for producing a wax coated nylon yarn withunclogged openings comprising coating the yarn with a polyethyleneglycol ester of beeswax liquid at a temperature of from 50° to 80° C.,removing excess portions of the liquid, and cooling the coated yarn to atemperature below 50° C. The liquid can optionally contain a flavoringoil, silicone oil lubricant, or mixtures thereof.

The products of these processes are also aspects of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representation of the relaxed dental floss brush of thisinvention.

FIG. 2 is a representation of a continuous length of relaxed, connecteddental floss brushes of this invention.

FIG. 3 is a schematic representation of the system for producing acontinuous length of connected dental floss brushes of this invention.

FIG. 4 is a schematic representation of a portion of the drier andheater assembly shown in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

The elongate teeth cleaning article of this invention provides thecombined functions of an interproximal brush and floss. In therepresentation shown in FIG. 1, the polymer coated thin floss brush 2comprises a brush portion 4 positioned between terminal thread portions6 and 8 integral therewith. The brush is relaxed and yarn-like, suitablefor cleaning between the teeth in a brushing action, pulling the flossback and forward across tooth and gingiva surfaces. The cavities in thebrush surface capture and remove food, bacteria and other materials onthe tooth and gum surfaces. Under tension, the brush portion stretchesto become a thread, suitable for the upward and downward scraping motionalong the opposed tooth surfaces and facilitates easier insertionbetween interstitial spaces. When relaxed, the brush portion returns tothe yarn-like extended configuration.

The thin floss brush 2 is manufactured in a continuous length ofalternating thread and brush portions, a portion of which is shown inFIG. 2. By severing the thread portion 10 separating a terminal threadand brush portion 12, a length of floss corresponding to FIG. 1 isobtained. This continuous length of floss is suitable for dispensingfrom a spool in a conventional floss dispenser.

FIG. 3 is a schematic representation of the system for producing acontinuous length of connected dental floss brushes of this invention.The article is manufactured by processing a yarn, preferably a hightenacity nylon yarn, with a polymer coating, evaporating solvent fromthe thread portions under tension, steam treating the relaxed yarn,removing excess solvent and evaporating residual solvent, and optionallycoating the yarn with a low melting, non-clogging wax coating followedby removing excess coating and cooling the yarn. The product is thencollected on reels (spools or cones) which are further processed througha packaging operation to provide the finished output product.

Yarn 20 is drawn from yarn packages (spools or cones) which is mountedon a creel 22. Yarn 20 is pulled through the coating bath 26. In coatingbath 26, a polymer solution in a volatile solvent is applied to the yarnwhile the tension is increased, effecting liquid penetration of the yarnwhile avoiding excessive liquid pickup. Any excess coating solution isremoved by conventional squeeze rollers. The coated yarn is thentransported through a device that applies a dye to a selected segmentsuch as the thread section.

The coated, dyed yarn is then pulled into a chain driven drying chamber28. Referring to FIGS. 3 and 4, this system comprises opposed movingchains 30 and 32, the opposing faces of each moving chain havingrespective insulating pads 34 and 36. The upper chain sections includeinfrared heaters housed in a stainless steel vestibule. The lower chainsection includes an air exhaust vestibule. The combination of the forcedconvection and radiant heat evaporates solvent which is removed from thedriving chamber through the air exhaust vestibule 40. The portions ofthe yarn suspended between and shielded by adjacent insulating pad pairsin heating zones 42 are exposed to the heat, and the exposed coating iscompletely dried and hardened (the solvent is substantially vaporized)by the time it reaches the exit of the drying chamber. The exposed,dried portions retain the thin configuration formed under tension,producing the thread portion. The portions of the yarn held between theinsulating pads 34 and 36 are protected from the heat and experiencelittle or no solvent loss during the period of high tension. Theinfrared heaters are designed and arranged to provide dryingtemperatures of from about 70° to 160° C.

The yarn is then passed under relaxed conditions (i.e., low or zerotension) into a steam treatment chamber 44. When the yarn tension isrelaxed after emerging from the heater section 28, these undriedportions partially contract to a partially bulked configuration. Insteam chamber 44, the brush portions are exposed to substantiallysaturated steam having a temperature within the range of from 80° to105° C. until the brush portions almost completely contract andsubstantially regain the original puffiness and bulked condition of theinitial uncoated, relaxed yarn. This is usually achieved by a treatmentof 3 seconds and longer, depending upon the nature and level of coating.

The rebulked, steam-treated floss is then passed into roller drivendrying chamber 46. The residual liquid (solvent and water) is evaporatedby conduction and convection heat transfer using heated air having atemperature within the range of from 150° to 200° C. and a flow rate of150 to 300 cfm. Air is supplied through manifold 50 and vapors areremoved through exhaust system 48.

The continuous length of floss brush can be collected on reels as anunwaxed floss product at this stage.

Optionally, for producing a waxed floss brush, the solvent-free floss ispassed through a wax coating bath 52 where a low melting wax coating isapplied at an elevated temperature. The excess wax coating is removed bypassing the floss brush between squeeze rollers, and the continuouslength of floss brush is passed into the refrigeration or coolingstation 54. Passing through a gas stream produced by blower 56, solventsare evaporated and the vapors removed through exhaust manifold 58. Thewax coated product is then collected on reels (spools or cones) in thecollecting station 60.

The floss brush is then rewound from the spools or cones ontoconventional individual dispenser spools.

Most textured nylon yarns were found to lack the tensile strengthrequired for this process. The products of most bulking processes lackthe aesthetic appeal required for this product, i.e., wild strands,broken filaments, etc. False twist texturizing provides the mostsatisfactory aesthetic appearance. For making a thin floss brushproduct, use of yarn having a lower decitex is required withoutsacrificing strength.

False twisting gave an acceptable aesthetic product, but strength wasfound to be limiting. During texturizing, the yarn is subjected toextreme heat, reducing its strength. For yarns prepared by twistingtogether an uneven number of ends (such as five 2×2×1), often one endfailed under tension, reducing the overall strength of the yarn. Wefound that by controlling the heat to avoid damaging extremes, a falsetwisted product having the required strength could be obtained.

The steaming process increased bulk of the yarn, yielding a productwhich slips easily between teeth under tension and which bulks up to beused either as a floss, cleaning by scraping up and down, or by linearmovement as a brush. The bulked portion is easier on the gums. Theproduct can accept liquid or solid flavoring materials because of itsopen mesh structure and increased surface area over regular floss. Thisprovides a product with a more lasting flavor and increased customerappeal.

Reverse or false twisted, high tenacity nylon yarn having a breakingstrength of at least above 5N, preferably above 20N and optimally above35N was found to be satisfactory. These yarns are formed by firsttexturizing a high tenacity nylon yarn using a conventional pin-twistingprocess, using only sufficient heat required for the texturizing andavoiding temperatures which will significantly damage the yarn and itsfilaments and reduce their strength. Left and right pin-twisted strandsare then combined to form the final reverse-twisted, textured yarnproduct. A suitable yarn is available from Chapman Fraser & Co. Ltd.Thurmaston, Leicester, England.

The polymer solution applied in coating bath 26 can be a solution oremulsion of a nylon, polyurethane or mixtures thereof. Suitable nylonsolutions in lower alkanols of the types conventionally used in coatingdental flosses are suitable. An example is the GENTAL™ alkanolic nylonsolutions (General Plastics Corporation, Bloomfield, N.J.). Preferredpolyurethanes are water dispersible urethanes such as the anioniccolloidal urethane elastomer dispersions sold under the tradenameSPENSOL® polyurethane dispersions (Spencer-Kellog Products). Optimally,the coating solution or emulsion is a mixture of from 5 to 15 percent ofalkanol-soluble nylon and from 5 to 15 percent water-dispersiblepolyurethane in a mixed water/alkanol solution such as a water/ethanolsolution such as a mixture of 75 wt.% of GENTAL™ A151A alkanolic nylonsolution and 25 wt % of SPENSOL®L54 aqueous polyurethane dispersion.

Application of conventional microcrystalline waxes or polyethyleneglycol waxes to nylon yarns clog the spaces of the yarn and make itineffective for use as a brush. We have discovered, however, that heatedliquid polyethylene glycol esters of beeswax can be use to coat suchyarns, and if the excess is removed before cooling, only the individualfilaments of the yarn are coated and most of the original yarn textureand cleaning ability is retained.

The heated polyethylene glycol esters of beeswax have a low meltingtemperature, usually within the range of from 65° to 70° C., and aremutually soluble with flavor oils. They therefore provide a suitablevehicle for applying flavoring to the floss brush. They also function asemulsifiers and surfactants and can be combined with alkanolic oraqueous solutions of sweeteners such as saccharine, cyclamates orxylitol and with lubricants such as silicone oils. Preferred low meltingwax coating compositions are esters of polyethylene glycols having anaverage molecular weight of 300 and beeswax. Preferred coatingcompositions containing liquid flavors (A) and a mixture of liquid andencapsulated flavors (B) are shown in the following table.

    ______________________________________                                        FLAVORED WAX COATING COMPOSITION                                                                    Amount, wt. %                                           Component               A      B                                              ______________________________________                                        Polyethylene glycol ester of beeswax.sup.a                                                            36.0   30.5                                           Silicone oil lubricant.sup.b                                                                          27.0   25.0                                           Mint flavor.sup.c       34.0   26.0                                           Spearmint cap..sup.d           4.0                                            Peppermint cap..sup.e          12.0                                           Saccharin               0.6    0.5                                            Ethanol, 96%            2.4    2.0                                            ______________________________________                                         .sup.a ESTOL E03BW 3751, Unichema International                               .sup.b DOW CORNING 200 Fluid, 350 cSt                                         .sup.c Noville Fragrance #62082                                               .sup.d Encapsulated Spearmint Borden# 13587                                   .sup.e Encapsulated Peppermint Borden# 137422                            

Although preferred embodiments of the subject invention have beendescribed in some detail, it is understood that obvious variations canbe made without departing from the spirit and the scope of the inventionas defined by the appended claims.

The invention claimed is:
 1. A continuous length of dental flosscomprising alternating sequences of thread portions and floss brushportions integral therewith as manufactured by a process comprising thesteps ofa) coating a reverse twisted high tenacity nylon yarn with asolution of polymer in a volatile solvent, the polymer being selectedfrom the group consisting of nylon, polyurethane and mixtures thereof;b) selectively vaporizing solvent from thread portions of the yarn andpreventing significant vaporization of solvent from brush portions ofthe yarn while the yarn is maintained under a tension of at least 0.15N;c) bulking up the brush portions by exposing the brush portions of theyarn to steam while the yarn is under a tension of approximately zero;and d) removing residual solvent from the brush portions of the yarnwhile the yarn is under a tension of approximately zero.
 2. A continuouslength of dental floss of claim 1 wherein the dental floss is made froma reverse twisted, high tenacity nylon yarn comprising at least twothread sections having diameters, in their relaxed state, of less than2.5 mm, the thread sections being separated by a floss brush sectionintegral therewith of yarn having a diameter of up to 4 mm in itsrelaxed state, and a reduced diameter when placed under tension, thefloss brush having a breaking strength of at least 5N.
 3. A continuouslength of dental floss of claim 1 wherein the reverse twisted hightenacity nylon yarn has a breaking strength of at least 20N.
 4. Acontinuous length of dental floss of claim 1 wherein the thread sectionshave diameters, in their relaxed state, of less than 50 percent of thediameter of relaxed, uncoated yarn from which they were formed.
 5. Acontinuous length of dental floss of claim 1 wherein each floss brushsection has a diameter under a tension of 0.05N of at least 60 percentof relaxed uncoated yarn from which it was formed.
 6. A continuouslength of dental floss of claim 1 wherein the floss brush is coated witha low melting wax composition.
 7. A continuous length of dental floss ofclaim 6 wherein the wax composition consists essentially of polyethyleneglycol ester of beeswax.
 8. A continuous length of dental floss of claim6 wherein the wax composition is mixed with a flavoring oil, siliconeoil lubricant or mixtures thereof.
 9. A continuous length of dentalfloss of claim 1 wherein the solution of polymer in the process containsfrom 5 to 15 wt. % polyurethane composition and from 5 to 15 wt.% nyloncomposition.
 10. A continuous length of dental floss of claim 1 whereinthe solvent in the process is an aqueous ethanol solution containing atleast 57 wt.% ethanol.
 11. A continuous length of dental floss of claim1 wherein the steam in the process has a temperature of from 80° to 105°C.
 12. A continuous length of dental floss of claim 1 wherein thesolvent is selectively vaporized from thread portions of the yarn byexposing the thread portions to heat while shielding the brush portionsadjacent thereto with heat insulators.
 13. A continuous length of dentalfloss of claim 1 wherein the process includes the additional steps ofcoating the threads of the brush portion of the product of step (d) witha low melting wax without permanently clogging the openings thereof. 14.A continuous length of dental floss of claim 13 wherein the low meltingwax is a polyethylene glycol ester of beeswax having a temperature offrom above 50° up to 80° C., excess portions of the wax is removed, andthe coated brush portions are cooled to a temperature below 50° C.
 15. Acontinuous length of dental floss of claim 13 wherein the low meltingwax is mixed with a silicone oil lubricant, flavoring oil or mixturesthereof.